This working paper by two Dutch researchers, while not focused on the Americas, nevertheless offers interesting insights into how technology is affecting migration. From the International Migration Institute at the University of Oxford. [link]

Immigration Statistics for the 21st Century

By Douglas S. Massey, a professor of sociology and the Director, Office of Population Research, Princeton University. [link]

Mapping the Effects of Climate Change on Human Migration and Displacement

A study by experts from the UN, CARE International and Columbia University. [link]